thulium
noun
thu·li·um
ˈthü-lē-əm 
ˈthyü-
: a soft silvery metallic element of the rare-earth group see Chemical Elements Table
Examples of thulium in a Sentence
Recent Examples on the Web
Advertisement The ministry also announced on Thursday curbs on more rare earths and related products, including holmium, europium, ytterbium, thulium, and erbium, effective Nov. 8.
—
Miranda Jeyaretnam, Time, 13 Oct. 2025
In its most recent move, China added five rare-earth elements – holmium, erbium, thulium, europium, ytterbium, and related magnets and materials – to its existing control list, requiring export licenses.
—Ramishah Maruf, CNN Money, 11 Oct. 2025
Set up with a mass spectrometer called FIONA, the apparatus can create heavy elements by firing a beam of calcium isotopes into a target of thulium and lead.
—David Szondy
august 27, New Atlas, 27 Aug. 2025
The extra proton changes the erbium atom to thulium and release energy.
—Bayarbadrakh Baramsai, IEEE Spectrum, 27 Feb. 2022
The least abundant of these, thulium (Tm) and lutetium (Lu) are 200 times more abundant than gold.
—Willy Shih, Forbes, 24 Feb. 2021
The 794 nm photon interacts with a lithium-niobate crystal doped with thulium, so that the photon’s state becomes stored in the crystal.
—Anil Ananthaswamy, Scientific American, 19 June 2019
Even the rarest rare earth, thulium, with atomic number 69, is 125 times more common than gold.
—Stanley Merzman, Discover Magazine, 21 Aug. 2018
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Miranda Jeyaretnam, Time, 13 Oct. 2025
In its most recent move, China added five rare-earth elements – holmium, erbium, thulium, europium, ytterbium, and related magnets and materials – to its existing control list, requiring export licenses.
—Ramishah Maruf, CNN Money, 11 Oct. 2025
Set up with a mass spectrometer called FIONA, the apparatus can create heavy elements by firing a beam of calcium isotopes into a target of thulium and lead.
—David Szondy
august 27, New Atlas, 27 Aug. 2025
The extra proton changes the erbium atom to thulium and release energy.
—Bayarbadrakh Baramsai, IEEE Spectrum, 27 Feb. 2022
The least abundant of these, thulium (Tm) and lutetium (Lu) are 200 times more abundant than gold.
—Willy Shih, Forbes, 24 Feb. 2021
The 794 nm photon interacts with a lithium-niobate crystal doped with thulium, so that the photon’s state becomes stored in the crystal.
—Anil Ananthaswamy, Scientific American, 19 June 2019
Even the rarest rare earth, thulium, with atomic number 69, is 125 times more common than gold.
—Stanley Merzman, Discover Magazine, 21 Aug. 2018
Cite this Entry
“Thulium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/thulium. Accessed 30 Oct. 2025.
Copy CitationKids Definition
thulium
noun
thu·li·um
ˈth(y)ü-lē-əm
: a soft rare metallic element see element
Medical Definition
thulium
noun
thu·li·um
ˈth(y)ü-lē-əm
: a trivalent metallic element of the rare-earth group
—symbol Tm
see Chemical Elements Table
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